This invention relates to a lighting peg which is installed, for instance, at the center of road intersections along the center line of roads or in vehicle stop lines where vehicles stop temporarily.
Heretofore, various devices for the above described use have been proposed. One such device is an automatic flashing lamp for indicating the edges (or shoulders) of roads, where a first photoelectric conversion element senses the ambient light, while a second photoelectric conversion element senses the light from a vehicle, has been disclosed in Japanese Utility Model Publication No. 39915/1977. Also proposed is a road marking device wherein the ambient light is detected from the output voltage of a solar cell, while the light from a vehicle is sensed by a photoelectric conversion element, and a pulsating light emitting diode is thereby operated (refer to Japanese Utility Model Laid-Open Publication No. 68113/1986). Also proposed is a marking plate wherein a photoelectric conversion element is utilized, and when the element receives light from a vehicle at night, an oscillator operates a light-emitting diode in a pulsating manner, but when light is continuously received in the day time or at night, a counter provided therein turns off the light-emitting diode (refer for instance to Japanese Utility Model Laid-Open Publication No. 95686/1985 which was filed by the applicant of this invention).
However, according to the sensing method of the first and second conventional devices mentioned, the operation tends to be delayed or made inoperative even at night, if there are street lamps or the like provided nearby the device, and also in cases where the weather is cloudy or the area is dark. Otherwise, when the sensible distance of vehicle light has been set to be long, erroneous operation tends to occur in the evening unless the photoelectric element is adjusted to be operable in comparatively dark conditions. Furthermore, when the device comprises serially connected analog circuits composed of transistors or the like, the two photoelectric conversion elements provided in the device tend to interfere with each other in the low illumination region, thus rendering adjustment extremely difficult.
According to the third conventional technique mentioned, although no erroneous operation due to the ambient condition has been recognized, the setting of the detectable distance of an incoming vehicle requires the adjustment of variable resisters with a model vehicle having its lights turned on and positioned at a predetermined position. Furthermore, the detectable distance thus set does not always correspond to the practical value because the light of a vehicle is not always of constant brightness.